1. Field of the Invention
The present invention relates to a process for preparing a phosphoric ester. More specifically, the present invention relates to a process for preparing a phosphoric ester which is useful for, for instance, a shampoo, a cleaning agent, a facial cleansing agent, an emulsifier, and the like.
2. Discussion of the Related Art
A phosphoric ester of an organic hydroxy compound (hereinafter also referred to as xe2x80x9cphosphoric esterxe2x80x9d) has been used in the field of a cleaning agent, an emulsifier, a fiber-treating agent, an anticorrosive agent, pharmaceuticals and the like. Especially, an alkali metal salt such as a potassium or sodium salt of a monoalkyl phosphoric ester having a long-chain alkyl group, and an alkanolamine salt such as triethanolamine are useful for articles which are directly used for human bodies, such as a shampoo and a facial cleansing agent, because they have water solubility, are excellent in foaming power and detergency, and exhibit low toxicity and low skin irritability. When the phosphoric ester is contained in the articles which are directly used for human bodies, weak odor is required for the phosphoric ester in its quality.
The phosphoric ester has been prepared by reacting an organic hydroxy compound with a phosphorylation agent such as phosphorus pentoxide, polyphosphoric acid or phosphorus oxychloride. However, there exist as impurities in the phosphoric ester an unreacted organic hydroxy compound and a by-product such as an olefine generated during the phosphorylation reaction. These impurities may give wrong influence to the phosphoric ester because the impurities act as odorous components, so that a complicated process for removing the odorous components would be necessitated after the reaction.
As a deodorization process for removing impurities such as an organic hydroxy compound, there have been proposed a process comprising re-crystallizing with a solvent to remove impurities from the phosphoric ester as disclosed in Japanese Patent Laid-Open No. Hei 11-158193, and an extraction process comprising reacting a phosphoric ester with a basic compound to give a salt of the phosphoric ester, and extracting odorous components to an organic layer and the salt of the phosphoric ester to an aqueous layer with a solvent as disclosed in Japanese Examined Patent Publication No. Hei 03-027558.
However, according to these processes, since the solvent is used in a large amount, there is necessitated an equipment for collecting the solvent. In addition, according to the process comprising recrystallizing the phosphoric esters to remove impurities, when the phosphoric ester is a phosphoric ester having a distribution in an alkyl moiety or a phosphoric ester having a distribution in the number of moles added of the alkylene oxide adduct is used, the distribution states of the alkyl moiety or the alkylene oxide adduct of the phosphoric ester after the treatment would change from that before the treatment, so that a problem would be caused in the preparation of a product, and moreover the loss of a solvent used for the phosphoric ester is unavoidable. Also, according to the extraction process, a complicated process for collecting a solvent is necessitated because this process requires a lower alcohol as a demulsifier besides the extraction solvent, and as a result, investment costs for its equipments would be increased.
As described above, there are some defects in the processes using a solvent such that the productivity is lowered, and investment costs for equipments are increased, so that necessary costs become higher.
On the other hand, as a deodorization process using no solvent, there have been proposed a process comprising contacting a phosphoric ester with an inert gas including steam with a rotary thin-film-type evaporator, or a thin-film deodorizing tower such as a wet wall tower as disclosed in Japanese Examined Patent Publication No. Sho 62-025155, and a process comprising carrying out phosphorylation reaction with blowing steam into raw materials as disclosed in Japanese Examined Patent Publication No. Hei 05-066958.
However, when odorous components are removed by blowing an inert gas with a rotary thin-film-type evaporator, or a thin-film deodorizing tower such as a wet wall tower, since the contact area between the vapor phase and the liquid phase is smaller as compared to the size of the whole apparatus, the contact efficiency is lower, a larger amount of the inert gas is required, and the apparatus becomes larger, so that the investment costs for the equipment become larger, thereby increasing the cost. In addition, since the amount of waste water or the amount of exhaust gas is increased, the treatment costs would be increased.
In addition, when steam is blown into the raw materials during the phosphorylation reaction, phosphorus pentoxide or polyphosphoric acid which is a phosphorylation agent having a pyrophosphate bond would be decomposed by steam, thereby inhibiting the reaction with the organic hydroxy compound. Therefore, the amount of an unreacted organic hydroxy compound increases, and a wrong influence is given to odor.
Therefore, it has been earnestly desired to develop an industrial process for economically and advantageously preparing a phosphoric ester having reduced odor, capable of easily reducing odorous components remaining in the phosphoric ester.
An object of the present invention is to provide a process capable of easily and rapidly preparing a phosphoric ester having reduced odor.
These and other objects of the present invention will be apparent from the following description.
According to the present invention, there are provided:
(1) a process for preparing a phosphoric ester having reduced odor, comprising contacting a phosphoric ester with at least one of an inert gas and steam at 100xc2x0 to 160xc2x0 C. in a packed tower;
(2) a process for preparing a phosphoric ester having reduced odor, comprising repeating a set of processes comprising:
(A) heating a phosphoric ester, and contacting the heated phosphoric ester with at least one of an inert gas and steam; and
(B) cooling the phosphoric ester obtained in the step (A);
(3) a process for preparing a phosphoric ester having reduced odor, comprising adding water to a phosphoric ester, and distilling water from the phosphoric ester under reduced pressure; and
(4) a process for preparing a phosphoric ester having reduced odor, comprising reacting an organic hydroxy compound with a phosphorylation agent, while introducing an inert gas into the mixture of the organic hydroxy compound and the phosphorylation agent.